In general, basic processing steps of color light-sensitive materials include color development processing and desilvering processing. In the color development processing step, an exposed silver halide is reduced by a color developing agent to form silver and, at the same time, the oxidized color developing agent reacts with a color former (coupler) to provide a dye image. In the subsequent desilvering processing step, the silver formed by the development is oxidized with a bleaching agent and then converted to a soluble silver complex by the action of a fixing agent, which is then dissolved and removed.
In order to maintain photographic or physical qualities of an image or improve preservative property of an image, development processing further includes, in addition to the above-described basic steps, various auxiliary steps, such as hardening, stopping, image stabilization, washing, and the like.
In recent years, rapid processing, i.e., reduction of the time required for processing has been highly demanded. Reduction in the time for desilvering that occupies nearly half of the overall processing has been a particularly great subject of study.
One conventionally known means for achieving rapid desilvering is a bleach-fix bath containing both an aminopolycarboxylic acid iron (II) complex and a thiosulfate as disclosed in German Pat. No. 866,605. According to this technique, however, since an aminopolycarboxylic acid iron (II) complex having a weak oxidative effect (bleaching power) by nature is copresent with a thiosulfate having a reducing power, the bleaching power of the complex becomes too weak to effect sufficient desilvering for photographic color light-sensitive materials of high sensitivity and of high silver content. On the other hand, it has been proposed to enhance the bleaching power by adding various bleach accelerators to a bleaching bath or a bleach-fix bath. Examples of such bleach accelerators include various mercapto compounds as described in U.S. Pat. No. 3,893,858, British Pat. No. 138842 and Japanese Patent Application (OPI) No. 141623/78 (the term "OPI" herein used means a "published unexamined Japanese patent application"), compounds having a disulfide linkage as described in Japanese Patent Application (OPI) No. 95630/78, thiazolidine derivatives as described in Japanese Patent Publication No. 9854/78, isothiourea derivatives as described in U.S. Pat. No. 4,144,068, thiourea derivatives as described in U.S. Pat. Nos. 3,617,283 and 3,809,563, thioamide compounds as described in Japanese Patent Application (OPI) No. 42349/74 and dithiocarbamic acid salts as described in Japanese Patent Application (OPI) No. 26506/80.
Nevertheless, incorporation of these bleach accelerators into a bleaching bath, a bleach-fix bath or a prebath therefor is still insufficient for establishment of rapid processing, and further improvements have been demanded.